1. Field of the Invention
The present invention relates to a communication system, and more specifically, to a multi-carrier communication system.
2. Description of the Prior Art
In a general communication system, such as a multi-carrier communication system, if there is interference occurring in a channel between a transmitter and a receiver, the interference will influence signals that will be transmitted to the receiver. Therefore, the signal received by the receiver is a mixed signal of the signal transmitted by the transmitter and an interference signal. In order to eliminate the above-mentioned influences on the received signal, an equalization circuit and a channel estimation circuit are installed in the receiver. The channel estimation circuit is utilized for estimating the weakening and interference resulting from the channel of the received signal according to preamble symbols in the received package. Because the preamble symbols are a series of known symbols, the influence degree of the channel (represented as a channel estimation value) can be determined by comparing the received signal and the known symbols. The operation of the conventional channel estimation circuit is described in the following equation (1):
                    H        =                  R          X                                    Equation        ⁢                                  ⁢                  (          1          )                    
Where R denotes the received signal, X denotes the known preamble symbol(s), and H denotes the above-mentioned channel estimation value. Next, the equalization circuit processes the received signal R using the channel estimation value H to render an equalized signal. The equalized signal is viewed as a reconstructed signal in which the channel responses are eliminated, and also approximates the signal transmitted by the transmitter.
In fact, a wireless communication system may receive accidental interference from other wireless communication systems. At that time, a change of an external circumstance cannot be compensated for with only a channel estimation value. If there is an accidental interference occurring during the channel estimation operation, the channel estimation value generated by the channel estimation operation may have a serious error, and will further affect an equalized signal generated according to the wrong channel estimation value.